I have recently been having problems with my serpae tetra because he has not been swimming up right too. I have placed him in a container with holes in it and floating in my fresh water 20 gallon tank (the same tank). The weird thing was that my Golden X-Ray tetra was hitting it and nipping at him and my other serpae tetras. It gets to make me now think they are territorial. They are usually community fish so I do not understand why he is doing that. If any of you can help me figure out what is wrong with my serpae tetra and now why my golden X-Ray tetra is doing this. Please let me know. I will post some pictures along with this.

All shoaling fish are territorial to a degree. Their behaviour depends on how many of them there are, how many other species there are, whether any of the other species are a similar shape, what size their aquarium is, how old the fish are and what order they were added.

I have made my album UN private, and thank you for letting me know that it was because I recently just joined and didn’t know I had to turn off the private setting. The gold tetras I added first and they were in there for about a couple months. The Serpea Tetras I added recently, like 2 weeks ago. So the Golden X-Ray Tetras must be territorial because they were in there for way longer than the Serpea. I only have two of the Golden Tetras and three of the Serpea Tetras. My tank consists of 7 different species and 16 fish. The Serpea Tetras are the closest to their shape. The tank is a 20 gallon long. Thank you,Justin